Almost every airbag, in particular every front airbag, has a ventilation device through which gas can escape from the gas compartment enclosed by the outer shell of the gasbag—hereinafter first gas compartment—when the person to be protected impacts thereon, so that the kinetic energy of the person to be protected is dissipated, and the person to be protected does not simply rebound from the airbag shell of the airbag. In the simplest case such a ventilation device is merely a ventilation opening, in particular a ventilation opening in the airbag shell.
In order to take into account different accident situations and/or the weight of the person to be protected, adaptive influencing devices to influence the shape of the airbag or the pressure in the gas compartment have been known in the prior art. A detachable retaining strap may be provided if the shape of the airbag is to be influenced. Furthermore, adaptive ventilation devices are known that have a throttle element in addition to the ventilation opening which throttles the gas flow through the ventilation opening more strongly in a first state than in a second state. As a rule, in this case the first state is the throttled or even closed state, and the second state is the less throttled, by way of example, the completely open state.
In some such airbag modules having an adaptive influencing device, an actuation device is also provided, which makes it possible to actively change the influencing device from its first state to its second state when an external signal is given. By way of example, a pyrotechnic actuator for this purpose is known from U.S. Pat. No. 6,648,371 B2. In this case, the first end of a tensioning strap is connected to the throttle element, and the second end of this tensioning strap is connected to a bolt of the actuator. In this case, the actuator is, in particular, held to the bottom of the housing of the airbag module. As long as the actuator is not actuated, the throttle element is thus connected to the bottom of the housing via the tensioning strap. When the shell of the airbag is completely expanded, the tensioning strap is in a tensioned state which keeps the throttle element in its first state. When the actuator is actuated, the bolt holding the second end of the tensioning element is dislodged by means of a pyrotechnic load, the tensioning element loses its tension and the throttle element changes to its second, namely unthrottled state. This technique basically functions very well, but has the disadvantage that parts like the bolt can fly around inside the gas compartment of the airbag shell, and that open flames can occur inside the shell of the airbag due to the pyrotechnic load. Furthermore, the pyrotechnic load feeds additional gas into the gas compartment of the airbag shell, which is not always desirable.
The generic DE 10 2005 039 418 B4 proposes an airbag module with an adaptive ventilation device, in which the actuation unit is formed by a “small airbag module inside the airbag module”. In this case, the throttle element can be influenced by a second, small airbag inside the gas compartment of the actual shell of the airbag. The shell of this second airbag module—hereinafter the second shell—encloses a second gas compartment which can be filled with gas by a generator having the shape of a squib. If this occurs, the second shell filled with gas lifts the throttle element in the shape of a flap from the ventilation opening, so that the ventilation device changes to its second, unthrottled state. This has the disadvantage that the second shell and the ventilation opening must be immediately adjacent to one another, which is frequently only very difficult to realize. In particular, it is scarcely possible to provide the ventilation opening in the shell of the airbag.
On this basis, the object of the present invention is to further develop a generic airbag module such that a large structural and functional flexibility is provided. In the case when the adaptive influencing device is an adaptive ventilation device, it should, in particular, be possible to provide the ventilation opening in a section of the airbag shell. This airbag shell can be an outer shell, which separates the first gas compartment from the environment, or a partition shell that separates two chambers from one another. Hereinafter, this shell will therefore be referred to as the “first shell”.